Apparatus fob treating impure



D. C. REYBOLD ETAL I June 26, 1945.

APPARATUS FOR TREATING IMPURE LIQUIDS Original Filed Dec. 18, 1941 s Sheets-Sheet 1 INVENTORS June 26, 1945.. c REYBQLD ET AL Re. 22,652

APPARATUS FOR TREATING IMPURE LIQUIDS Origifial Filed Dec. 18, 1941 35heets-Sheet 2 ATTORNEY.

June 1945- D. c. REYBOLD ETAL Re. 22,652

APPARATUS FOR TREATING IMP URE LIQUIDS Original Filed Dec. 18, 1941 ATTORNEY.

maaa'rus Rs. 22,652 5' PATENT OFFICE roa 'rnna'rmc m mourns was. 0. Reybold, Northbrook, m, and Anthony J. Fiachen-Manhasset, N. 1., assignors to The Don Company, New York, N. Y., a corporation ware oIDela Orldnal No. 2,340,842, dated February. 1.19458 rial No. 499,812, August-24, 1943, which is a division of Serial No. 423,430,!Iecember 18, 1941.

Application for reissue August 29, 1944, Serial new.

This invention relates to the purification oi polluted or impure liquids such as sewage, tradewastes and the like, and this application is a division of application No. 423,430 filed December 18, 1941. In such purification, one recognized method in use today involves the use of a bed discrete material containing biological organisms which include a wide range thereof from bacterial flora up to animal iiie as exemplified by worms.

The, biological organisms are depended upon to convert the unstabl and putrescible or septical organics that render the liauid impure into stable innocuous substances. depended upon, at least in part, to render nonsettleable suspended solids more readily settle'able.

The invention has relation to what is known in the sanitary engineering art, as trickling filter- (Cl. arc-) .the rate of new feed incoming to the system. The new ieed may be introduced at any suitable point. Likewise, the eiliuent may be discharged from the system at any desired point.

Among other advantages realizable, mention is made or the fact that recirculating trickling filter systems gave the unexpected result of permittin the use of filter beds only three feet or less in a depth which could be operated at high efilciency.

This permits the use of high filter loadings figured as pounds of B. O. D. per cubic yard of filtering media per day. It has been found that The organisms are also beds. 0! late it has come to be accepted-that it is desirable to supp y liquid to be treated in filterbeds at rates that would have been considered a few years ago as dangerously high. This invention has especial application to high-rate filterbeds. An outgrowth of the high-rate filter-bed is that there be associated with it a recirculation system whereby liquid being treated can be repeatedly or continually recirculated through the filter-bed. This permits the continuous closing on the filter-bed of a liquid more uniform in character, and reduces the extreme fluctuations in fiow. Inmost systems one or-more detention tanks are associated with the filter and the recirculation system may be so arranged that filter eilluent is recycled back to the detention tank or primary clarifier preceding the filter; or deten-' tion tank or secondary clarifier effluent is recycled back to. the filter which preceeds the detention tank. In either case the filter is dosed at such a rate with liquid containing micro-organisms iavorable to the promotion oi optimum biological conditions in the filter bed that clogging oi the filter bed is avoided due to a continuous sloughing 03 of the solids that wouldnormally tend to accumulate. At the same time, the recirculation from the filter to the primary clarifier or from the secondary clarifier to the filter dilutes the strength of the liquid fed to the filter so that it becomes more amenable to treatment. The de* tention tank is usually provided with means for mechanically cl'eaning it of deposited sediment to guard against septicity'oi' the sediment, and the tank is one from whichoverfiows a clarified eitypes of trickling filter plants involving a filter and a clarifier in closed-circuit.

the rate of qter applicationmay be multiples oi In recirculation the eflloiency of recirculating type filters in creases as the amount of recirculation increases.

The high rates of dosing tend to prevent clogging of the interstices between the discrete stone particles of the filter media; ample food is brought to the immotile biologic organisms or the-bed; their excretions are washed away therefrom; and some oi the organisms are washed into the clariher so that biologic oxidizing activity of the septical organics is continued in the'clarifler in ad- I dition to the bed wh' e it its initiated. This method 01' operation al keeps downthe filterfiy nuisance and further keeps down the odor nuisance.

' The disadvantage of the use of such high recirculation rates, however, is that a large and-expensive piping system'is required to convey the clarifier eiiiuent to the trickling filter bed. otherwise a high loss 0! head will result, possibly requiring the pumping to the beds. 1

According to the-present invention a-liquid treating system is employed wherein a relatively shallow bed of discrete material is disposed in encircling arrangement with respect to aliquidreceiving tank of a type which may function as a clarifier. The tank is furthermore of a type hava ing supernatant outflow means disposed about and leading from the upper marginal regions thereof. Also according to the present invention such shallow bed of discrete material functions as a trickling filter-bed extending to an elevation whereby gravitating filter eflluent can be collected and, according to operative requirements, pumped back into the tank substantially against only a minimum or relatively low back pressure head. The top 01!. the filter-bed is disposedat. elevation suificiently low so that-there can always be realized a gravity flow oi clarified liquid iromthe supernatant outflow means, to wit,-irom ,the region.

about the upper marginal portion of the tank, and consequent spraying of the gravity-conveyed liquid over the trickling filter-bed in a relatively uniform distribution. The use 0! the encircling the clarifier.

launder of the a shallow bedencircling the tank with its surface lower than the liquid level in the clarifier tank assures the gravity feed to the filter-bed directed from the clarifier through a conducting and distributing means which may be relatively simple and of low cost. This may be through a means embodying a number of relatively uniformly but horizontally spaced individual pipes extending downwardly from the uper marginal regions of the tank and of which the pipes terminate in spray heads or other suitable liquid diffusing delivering means. Each of these pipes is prefertion of the liquid is effected into settled sludge and eiliuent.

The straight filter must be dimensioned and operated to effect as completely as possible the biological purification and coagulation of sewage impurities within the interval allowed, for a single passage through the filter. Thisiaecessitated a lar e vo ume of filter media and af-depth of the filter which was accepted to be iron-n36 to 12 feet. This depth was so much the standard that it becaine a custom with sanitary engineers in specifying filter loads or capacities, to disregard the factor of filter depth as a constant and refer to filter canacity in terms of area or horizontal expanse only. Then there was accepted for filter capacity or load the dimension "m. g. a. d3; that is, million gallons per acre per day. 1

Since the patentees are working essentially with a shallow filter-bed in circuit with a detention tank or clarifier, the invention has for one of its objects an arrangement for the proper integration of these elements while they are concentri'cally disposed. with, the clarifier or detention tank in the center and the filter-bed or beds Anothervobject is to modify this arrangement for two-stage treatment. vAnd a further-object is to provide means for returning the filter-bed discharge back to be mixed with the liquid in the clarifler tank. A still further object is to provide means in this assembly for thoroughly distributing over the filter-bed area, the liquid passing thereto. Another object is to make suchan. assembly into an esthetically attractive design, for sewage-treating plants are being located increasingly in-parks or other public spaces of municipalities that are more or less landscaped.

An additional object is the provision to a mullw tiple launder for the clarifier so that emuent for head. And a still further obiect is to devise apparatus [for dosing the filter-bed direct from a Inconnecticn with recirculation of liquid from the clarifier tank that is in circuit with the filterther object of this invention is to devise a subform Fig. 3 is a vertical sectional view"of a formsomewhat different from that shown in Fig. '2.

Fig. 4 is a detail of a submerged weir-e or launder employed in the form of Fig. 3.

Fig. 5 .is a vertical sectional view embodying primary and sec ndary stages each of which embodies certain important features of the form of apparatus shown in Fig. 2.

In Figs. 1 and 2 the reference numeral ll indicates generally a clarifier tank having a-wall section l2, a bottom or fioor section l3, an upstanding pier theft is hollow and has a bore l5 from which feed liquid for the tank II is emitted in a slotted section l8. l1 indicates a-baflie for deflecting the feed liquid and preventing short-circuiting. The pier l4 terminates in a platform l8 that supports a bull ring or gear-providing an anular tumtablelil that is rotated through the medium of a motor 20 and any necessary gearing. The motor is carried on a stationary member l8 extending upwardly from the platform I 8 through the turntable is as for ex-- ample accordingv to the teachings of the'Scott Reissue Patent Re. 20,072. Supported from the turntable I9 is a depending cage or drum 2| from which at the bottom thereof extend rake arms 22 that are equipped to impel sediment over the overflows a weir 25 that determines the liquid level in the tank, and passes into a launder 28 that encircle the tank. Associated with the first annular launder Isis a further annular launder 28 which makes with launder 2G a combined or double launder that has a common wall 28. Liqi uid flows from launder 26 at intervals around its length, through a. plurality of downfiow pipes 30, which may be controlled by valves .31, terminating in spray nozzles or other liquid distribution means 32 located'aiacent the .upper'surface of a trickling filter-bed 33 formed of discrete material or media 34 such as crushed stone or rubble that is supported from a permeable latticelike support 35 and a wall 38 that encircles the tank .H. The top of the filter-bed 33 is, lower than the liquidlevel of the tank I I. Liquid passes "from launder 28 through conduit 21 controlled by valve 21' to discharge or for further treatment. The floor 38 of the filter-bed .83 is'arrang'ed to drain filter-discharge into an annular trench or sump 88 that has associated with it a wet-well 40 from which filter discharge can be removed through pipe-ll bycentrifugalpump 42 which delivers into pipe 53 having a stop valve 53'. By closing stop valve 53' the filter eilluent can be passed from the filter throiigh a pipe equipped with stop valve 51' if and when the latter is open; or ii the stop valve 55' is open and the stop valve 51' is closed, then the pump 42 will force the filter eflluent into the pipe or conduit 43 thence into bore I of upstanding pier l4 so that the filter discharge re-enters the clarifier tank ii for retreatment therein. Filter discharge may be drained from the system as through avalve controlled pipe 44. 45 indicates a stop valve in pipe 43 and 55 indicates a check valve in pipe 43. This pipe 43 may be employed as means for passing newly incoming feed to clarifier tank II as well as part of'the means for passing filter eiliuent to the tank. 46 indicates a bridge or walkway for giving access to the operating parts of the tank ll.

Figs. 3 and 4 illustrate a modification or form which differs only slightly from that of Figs. 1 and 2. Where the parts are the same in each, the same reference numerals have been used and as to such like parts the previous descriptiveing feed liquid is supplied through the low pipe or conduit 43 thence to the bore I-5 of hollow pier 14 from whence it passes into the clarifier tank II. Clarified supernatant liquid is released from the tank by overflowing annular peripheral weir 25 into peripheral launder 25 from whence the liquid is released or passed outwardly through pipe 21. In this modification, the second launder is shown as a member 50 supported from the baffle l1. This second launder is in the form of a tubular collector or s'ubmerged'launder disposed below the liquid level of the tank II and is protected from scum and the'like by means of a top cover or strainer plate, 5| that is preferably perforated to let strained liquid fiow freely into the launder. As shown in Fig. 4, the top strainer plate 5| of launder 50 may also have associated with it a bottom strainer or perforated plate 5!. In fact, this second launder just described may be viewed as a submerged perforated collecting ring. From this submerged launder, liquid I passes at intervals through spaced-apart pipes 52 having valves 52' for controlling or adjusting the quantity of fiow to a distributing pipe 53 which is annular in plan and disposed adjacent the top of the filter-bed. This pipe. 53 is provided withsuitable overflow passage area as by being slotted at 54 from vwhich liquid is relatively uniformly distributed over the surface of the filter-bed 33. The centrifugal pump 42 returns filter-bed discharge through the valve-controlled pipe 56 to the low pi'pe or'conduit 43; It will be noted, however, that the discharge from the pump can be also pumped to release from the system through the valve controlled release pipe 51 having the stop valve therein. a

The quantity of normal supply of feed to the tank, to wit, the supply of fresh feed to the tank plus the returned or recycled filter eilluent passed by the pump.42 into the pipe or conduit 43, is greater than the quantity of liquid which is alliquid passing therefrom to and throughout the upper portion of the filter-bed 33 whereby the thus distributed liquid is caused to trickle downwardly within and throughout the entire bed.

Fig. 5 illustratesa two-stage plant of which the first or primary stage indicated at A is substantially the same as arrangement of Fig. 2. The

' secondary stage of this Fig. 5 is indicated at B from this bed passes into the sump 43, is pumped lowed to fiow into the submerged collecting ring and ultimately therefrom to and from the distributing pipe 53 and hence'the overfiowweir is enabled to function as a'means that deterto insure a relatively uniform distribution. oi!- are typified by the following:

Liquid to be treated passes inwardly throughand is a modified form of the design at A. As

to these two stages where the parts are the same i like reference characters have been employed.

In reference to stage B, it will be noted that normally the liquid is supplied thereto through conduit 31 into an outer launder 55. From this 32 by Which the liquid is distributed relatively uniformly over the top surface of the trickling filter-bed 33. The liquid trickling from the filterbed 33 is finally received as filter eflluent in the sump 40. From this sump of the secondary stage B filter effluent is passed by pump 42 into and through the conduit 43 and the hollow pier l4 whereby it is ultimately delivered into the liquidholding section of tank ll. tant liquid from this secondary tank ll overflows weir 25 into the innermost launder 26 from which it passes, or from which at least some of it passes through branch pipes by control valves 3| therein, into valve-controlled pipes 30 whereby it is distributed through the heads or members 32 of pipes 30.

It will be observed as to this secondary stage B that a partition member 29 is disposed between the innermost launder 25 and an intermediate launder 28. The top of this partition member 29 which i circular in plan or of other appropriate formation is at elevation lower than that of the overflow Weir 25 and serves to acts as an outlying second or intermediate weir that permits an overflow of some of the clarified effluent from within the launder 25 towards and into launder 28. From the latter launder 28 the effluent is passed to a region remote from the tank through the conduit or pipe 11. Operations than can be carried out in the apparatus in this two-stage conduit 55 past check valve 58' into conduit 43, thence upwardly through the hollow pier l4 of stage A whereby it is deivered into tank ll of stage A. The clarified liquid from this tank overflows weir 25 into launder 26 from which the overflow liquidor 'a controlled portion of the overfiowed liquid-passes downwardly through valve-controlled pipes by which-it is distributed over the trickling filter-bed 33. Efliuent therefrom by a pump 42 (a) through a valvecontrolled return branch 56, assuming the valve "is open, directly back into the tank ll of the first stage, or (b) into the transfer branch 50, if the valve 53 therein is open. whereby the filter efl'luent, or some of it, may be transferred directly into the pipe 31 leading to the second stage. In other words, at the option of the operator all. of the filter eflluent can be pumped through-branch 55 back into the tank, oronly a part of the filter eiiiuent will be pumped back into the tank; or none of .the filter effluent need he passed back into the tank of stage A, in other words, if the valve 56' of this return branch is closed, then all of the filter effluent can be passed by thepump 42 through the branch 64, assuming the valve 56 Clarified supernaplant of the latter is open. If valve 56' in the return branch'and if the valve 59 in branch 60 are only partially open, then it is possible to give a split passage of the filter effluent whereby some will I be returned to the tank I I and some will be transferred through .the branch 60 directly to the pipe 31 leading to the secondary stage B.

It will also be observed that the partion 29 between the inner and outer launders 26 and 28 is lower than theweir 25 whereby if desiredaccording to the position of the valves 3! in pipes Ell-none of the overflow past weir 25 will pass partition'29, or some portion of or all of the overflow past weir 25 can be caused to pass over the partition 29 as a secondary overflow into the outer launder 28 from which this twice overilowed liquor can pass through valve-controlled pipe 21 into pipe 3'! for gravity flow and delivery into the launder 66 of the secondary unit B. From the outer launder 6B the liquid is distributeddirectly over the filter-bed by the valvecontrolled pipes 30. Filter effluent is pumped from thesump 40 ofthe secondary unit into the tank H thereof. The clarified liquid from. a

this secondary tank ll overflows the weir and a portion thereof can be optionally passed treatment directly to the second stage wherebythe operations of the first stagelcan be eliminated and the trickling filter treatment can be carried outentirely at the second stage. Sludge from the tank of the second stage is passed by the pipe 24, pump GI and pipe 52 as return sludge that is delivered to a section of the pipe 43 leading to the primary stage.

With respect to the apparatus of Fig. 5, it has heretofore been pointed out'how the secondary stage can be employed as a single unit. It is now to be noted that the outer wall of the out-v lying launder 65 of the secondary stage B ex- I tends to an elevationhigher than that of the rising wall or partition between the outlying launder 66 and the intermediate launder 28. II

for any reason it is desired to temporarily employ only the primary stage A as a sludge treating unit this can be accomplished by closing valve I4" in the feed line leading to the tank of stage B and b closing the valves 3| and 3| of the pipes and 30' of stage B, allowing the efliuent to-pass from stage'A through the pipe 31 into the outlying launder of stage B, thence as overflow past the wall between the launders 28 and 66 and from the latter as efiluent released from the system through pipe 11.

In connection with each of the combined settling tanks and trickling filter-bed units shown in the drawings hereof, it will be noted that the depth of each tricklingfilter-bed is relatively shallow as compared with the depth of the tank. As shown the construction providing the bottom or floor of the trickling filter-bed is shown practically as an extension of. the bottom oi the tank.

With this arrangement a feed-supply pipe or influent conduit such as 43 can, without undue excavation, be located so as to extend directly below the floor of the filter as well as that of the settling tank.

The elevation of the top surface of each trickling filter-bed is substantially lower than that of the surf-ace level'of the liquid in the tank with which it is associated, or, as otherwise expressed, lower than the launders from which liquid is gravitationally passed through valve-controlled downfiow pipes such as 30 and 3| for d is=- tribution over the top of the bed.

In Fig. 3 the launder or submerged pipe from which the liquid is supplied to the bed through the valve-controlled downfiow pipes 52 is not disposed directly over the trickling .filter-bed.

However, it is locatedso that there is a gravital 'downfiow 'of liquid from,within the tankthrough the pipes 52 and ultimate distribution of the liquid over the bed. In the instance of each form illustrated the height'available for efiecting this gravitational transfer is substantially that dif ference in elevation between the upper surface of the trickling filter-bed on the one hand and the elevation or approximate elevation of the overflow weir 25. This difference in elevation or static head available is preferably of the order of from 3 to 4ft. of water.

The structure shown in Fig. 2 or the structure shown in Fig. 3 can be readily substituted for the corresponding subcombination shown in Fig. 5: 1

(a) By merely connecting the pipe2'l of either Figs. 2 or 3 to the pipe section 31 leading to the outside launder 66 of Fig. 5; and

(b) By substituting .for the curved portion or section 41! of the'pipe or conduit 43, of either Figs. 2 or 3, a T pipe section and valve substantially like that indicated in Fig. 5 by T pipe section 43* and the valve I4 With such changes it will be manifest how the apparatus .or structure of Figs. 2 or 3 can be operatively incorporated'in the arrangement of Fig. 5. While the launder or pipe 50 of Fig, 3 is submerged, it will be manifest that the gravitationalflow therefrom downwardly through the pipes 52 can be controlledas to quantity delivered to the trickling-filter bed served thereby by adjustng .thevalves 52' of said pipes, to wit,

' in a n. inner like that obtained by adjusting the valves 3! of Figs. 1, 2 or 5.whereby to control the quantity or rate of downward flow through the descending pipes 30. The valve control pipes 30 'of Figs. 1; 2 or 5 and the valve-controlled pipes 52 have corresponding functions and relationships.

We claim:

1. Apparatus for treating impure liquids com-' prising in operative combination a settling tank equipped with means for transferring sedimented material therefrom; a set of inner and outer margin-al'launders of which the inner launder is disposed for receiving as elliuent supernatant liquid overflowing from the tank and of which, the outer launder is disposed for receiving as splitoi'f eflluent a quantity of liquid overflowing from said inner marginal launder; a trickling filterbed of discrete material surrounding said tank; means providing a floor structure for said bed and having a sump for receiving filter eiiiuent gravitating thereinto; valve-controlled downflow means for passing liquid from said inner marsacs:

ing liquid from the outer launder along a pathway leading from the unit.

back to the tank and another serves to optionally conduct pumped liquid from the unit.

3. Apparatus for treating impure liquids com-'- prisingin operative combination a settling tank having means for transferring sedimented material therefrom; means associated with said tank providing inner, intermediate and outer marginal launders of which the inner launder is disposed for receiving as eflluent supernatant liquid overflowing from said tank, of which the intermediate launder is disposed for receiving as splitoff eiiiuent a quantity of liquid overflowing fromthe inner launder, and of whichthe outer mar- .tank is transferred from the inner launder and distributed over the trickling filter-bed; means for passing filter eiiluent from the sump to the tank: and means leading from said intermediate -launder for releasing liquid as treated eilluent leaving the unit.

4. Apparatus for the treatment of impure liquids polluted with septical organics comprising a mechanically cleaned clarifier provided with a sediment discharg outlet; means for supplying impure liquid to the apparatusmeans'determining the liquid level in the clarifier, launder means for receiving liquid from the clarifier, outlet means for releasing treated eiliuent from the apparatus. a trickling filter-bed having a bottom that supports discrete filter media annularly disposed around the clarifler with the top of the filter media at a general elevation below. that of the liquid level in the clarifier, a sump section in said bottom wherein accumulates liquid that has trickled through the filter-bed; means for continually passing liquid from the sump section to the clarifler; 'and a plurality of flow pipes extending outwardly from the launder means to the filter-bed adapted to distribute liquid by gravity flow from the launder means substantially uniformly to corresponding areas of the filter bed,

said launder means comprising 'one launder to whichthe outlet means is connected and a second launder submerged in the clarifier liquid from which clarifler liquid passes to'the filter-bed through said gravity flow pipes.

5. Apparatus for thetreatment-of impure liq-j uids polluted with septioal organics comprising a treated eiliuent from the apparatus, a trickling filter-bed having a bottom that supports discrete filter media annuiarly disposed around the clariner withthe top of thsfllter media at a general elevation below that of the liquid level in the clarifler, a sump section in said bottom-wherein accumulates liquid that has trickled-through the filter-bed: means for continually adding liquid 5 from the sump section to the clarifler; and a plurality of flow pipes extending outwardly from the clarifierto the filter bed adapted to distribute liquid by gravity flow from the launder means substantially uniform'lyto corres'ponding'areas of the filter bed, in which apparatus launder means extend marginally along the top portion of the clarifler and comprise a partitioning wall rising from the bottom of the launder and terminating at an elevation lower than the'overflow level of the clarifler, said partitioning wall defining an inner and an outer launder section, the inner launder section adapted to receive the primary overflow from the clarifler and having connected therewith saidpipes for passing clarifler g eflluent liquid by gravity flow to the filter bed,

said outer launder section being adaptedto receive excess clarified liquid overflowing said partitioning wall from said inner launder section and being connected with said efiluentoutlet means.

6. Apparatus for treating impure liquids com,- prising in operative combination a primary and a secondary station; (a), of which the, primary station includes a settling tank equipped with mean for transferring sedimented material 3 therefrom, a set of inner and outer marginal launders of which the inner launder is disposed for receiving liquid overflowing from the tank and of which the outer launder is disposed for receiving a quantity of liquid overflowing from said inner launder, a trickling filter-bed of discrete material surrounding said tank, means providlng a floor structure for said bed and having a sump for receiving filter discharge gravitating said secondary station includes a secondary settling tank equipped with means for transferring sedimented material therefrom; a set of inner, intermediate and outer launders of. which the innet launder is disposed for receiving a liquidoverfiowingtfrom the secondary tank, of which the intermediate launder'is disposed for receiving as split-ofl eflluent a quantity or liquid overflowing from the corresponding inner launder, and of which the outer launder is functionally separated from'the intermediate launder, a secondary trickling filter-bed of discrete material surrounding the secondary tank, means providing a fioor structure for said secondary filter-bed and having a sump for receiving filter discharge gravitating thereinto,- means-leading fromthe outer launder oi'the secondary unit and for distributing the liquid over the secondary trickling "filter-bed, means leadins from the inner launder 79 of the secondary unit and for distributing the liquid conveyed thereby over the secondary trickling filter-bed, and transfer means for passing liquid from said secondary filter-bed sump into said secondary tank; said apparatus also comprising for conducting liquid from the the secondary tank.

outer launder of the primary station to the outer launder of the secondary station, and efiluent conducting means leading from the intermediate launder of the secondary station to a locality' outside of the apparatus.

7. Apparatus for treating impure liquids comthe clarifier tank, launder means for determining the liquid level in the tank and for receiving liquid overflowing therein from the tank, gravity operated flow means for conducting liquid from the launder means to thefilter-bed and for distributing such liquid thereoverysaid two stages being supplemented by means for supplying feed liquid to the tank of the primary stage, means for transferring liquid from the launder means of the primary tank to the launder means of the secondary tank, and means for releasing treated liquid from the secondary stage. I

8. Apparatus according to claim 7, having a conduit section leading from' said pump of the primary tank to said transfer means supplying 9. Apparatus according to claim 7, according to which there is provided a valve for shutting off any direct supply of incoming liquid to the primary tank and in which there is a conduit section leading from a portion of the feed-supply section in the tank located lower than the overmeans that is ahead of said valve and extending to the secondary tank wherebythe primary stage may be short-circuitedand whereby the secondary stage can be employed as an individual liquid treating stage.

10. Apparatus for the treatment of impure liquids polluted with septical organics comprising a clarifier provided with a sediment discharge outlet, a feed conduit for passing to .the interior of the clarifier impure liquids supp ied for treatment in the apparatus, a check valve in said feed conduit for permitting a forward flow through the feed conduit into the clarifier but for preventing a backward flow through the conduit, a supernatant liquid outlet means including a member that determines the liquidlevel in the olarifier,

a trickling filter functionally associated with the clarifier and embodying a bed of discrete material constituting a biologically active trickling filter bed and a bottom supporting said bed, a sump section in said bottom wherein accumulates liquid that trickles from the filter bed, afilter emuent transfer means comprising a pump for continually passing eilluent from the sump section and having a pump-discharge pipe connected for delivering the pumped eflluent into the feed conduit at the delivery side of thecheck valve thereof, and means for passing liquid from the 11. In combined apparatus of the class described for treating impure liquids including a trickling filterbed; a sedimentation tank for quiescent settling including a partially submerged feedwell within thetank, means for passing sediment from the tank, and efiiuent overflow means functionally and spacedly separate from said feedwell for determining the liquid level in the tank; means for passing discharge from said filterbed to the feedwell; and a feed conduit for passing to .the'feedwellimpure liquid supplied for treatment in the combined apparatus; the combinationtherewith of means for collectin substantially clarified bacterially-active filter- .bed-inoculating liquid having a submerged inlet fiow elevation of the overflow means but higher than that of the lower end of the feedwell while disposed in plan view in a region proximate the feedwellbut remote from the overflow means, and means adapted to pass liquid from the collecting means to and for treatment in the filterbed including a conduit extending from the collecting means to the outside of the tank.

12. Apparatus according to claim 11 wherein the liquid collecting means derives support from the feedwell.

13. Apparatus according to claim 11 wherein the liquid collecting means and the feedwell have a wall in common.

'14. In combined apparatus of the class described for treating impure liquids, including a trickling filterbed; a sedimentation tank for quiescent settling including a centrally located partially submerged feedwell within the tank, sediment-discharge means leading from the tank, sludge-moving means having sludge impelling elements rotatable in -.a closed horizontally extending pathway for passing sedimented sludge to said discharge means, means passing through the feedwell for rotating the sludge-moving means, and an efliuent launder functionally and spacedly separate from the feedwell and having an overflow edge determining the liquid level in the tank; means for passing filtered discharge to the feedwell: and a feed conduit for passing to thefeedwell impure liquid supplied for treatment in the combined apparatus: the combination therewith of means for collecting substantially clarified :bacterially-active filterbed-inoculating liquid having an inlet section submerged in the tank to an elevation lower than that of the overflow edge of the launder.but higher than the lower end of the feedwell while disposed in plan pass liquid from the collecting means to and for treatment inthe filterbed including a conduit section extending in the tank above the pathway of the sludge-moving means frrom the collecting means to the outside of the tank.

DOUGLAS C. REYBOLD. ANTHONY J. FISCHER. 

